As shown in FIG. 10, a hitherto known transfer press employable mainly for deep drawing operations is provided with a link driven type slide b adapted to be driven by a link mechanism on the upstream side as seen in the direction of transference of works (as represented by an arrow mark a) and an eccentric gear driven type slide (hereinafter referred to as an eccentric driven type slide) d adapted to be driven by an eccentric portion on the main shaft via a connecting rod on the downstream side.
With such conventional transfer press, a crank angle representative of the lower dead point of the link driven type slide b for deep drawing operation on the upstream side is deviated from a crank angle representative of the lower dead point of the eccentric driven type slide d by an angle in the range of 10.degree. to 20.degree.. For the reason, when the one slide has reached the lower dead point, the other slide has still a certain amount of gap between the upper die half and the lower die half.
In view of this fact, conventional die changing is achieved for two slides in such a manner that one of the dies is separately unclamped from the corresponding slide at the different time when the latter is lowered to its lower dead point. This leads to drawbacks that a long time is required for die changing and die changing operations are performed at a reduced efficiency.
The present invention has been made with the foregoing background in mind and its object resides in providing a method of changing dies for a press machine of the type including two or more slides of which lower dead point in terms of a crank angle is different from each other which assures that the dies on the slides can simultaneously be exchanged with another ones and a time required for die changing can be reduced substantially.